Research Projects

Durability or fatigue performance of a component is an essential design aspect in the mobility sector, along with other key factors such as crashworthiness and structural stability. One must consider the effect on fatigue performance when lightweight structure demands thinner sections. Traditional treatments for improving the fatigue performance of a part employ methods like shot peening, laser peening, surface hardening, etc. Often, these processes lack precise control and uniformity of the parameters which dictate the fatigue performance. Moreover, these processes also require the deployment of additional infrastructure in the manufacturing step, which is associated with a significant investment. Development of a novel micro-textured material is presented in this proposal, where arrays of micron-sized indentations (referred hereafter as micro-texture) are formed on the surface of a sheet metal component using press forming by a set of patterned dies and punches. It is hypothesised that the size effects arising due to the accumulation of geometrically necessary dislocations (GNDs) or the plastic strain gradient around the micro-texture may restrict the formation of slip bands, which are precursors to fatigue crack initiation. Additionally, compressive residual stresses associated with micro-texture forming can further delay fatigue cracking. Preliminary investigations suggest that enhanced fatigue life is obtained with this method, where a 200% increase in the fatigue life can be achieved. Moreover, the periodic array of micro-texture on the sheet surface provides better hydrophobicity, as observed from the preliminary results of the contact angle measurements, and could enhance the surface degradation property. Additionally, the process has the advantage of being readily adopted in the existing manufacturing set-up with only minor modifications. The objective of the current proposal is to study the effect of the key parameters of the micro-texture array (shape, size and spacing) and the material properties on the fatigue and surface degradation performance and also understand the mechanism of such enhancement through numerical simulations and lab-scale fatigue and related experiments on micro-textured specimens. The parameters of the micro-texture array will be optimised for maximum enhancement of fatigue life and experimentally validated for fatigue performance under uniaxial and bending loads. The process can be beneficial for components where fatigue life is crucial, such as automotive wheels, leaf springs, mounting brackets and many other relevant parts in the mobility and defence sector.